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Chatterjee D.,Indian Central Mechanical Engineering Research Institute
International Communications in Heat and Mass Transfer | Year: 2014

We establish through numerical simulation a dual role played by the superimposed thermal buoyancy in controlling the boundary layer separation around bluff obstacles. The work essentially demonstrates the influence of superimposed thermal buoyancy on flow around bluff obstacles of circular and square cross sections in aiding/opposing and cross buoyancy configurations. For the aiding/opposing configuration we show two phenomena such as the suppression of flow separation which occurs at relatively low Reynolds numbers (10-40) and the suppression of vortex shedding at a moderate range of Reynolds numbers (50-150). In the cross buoyancy configuration, the initiation of vortex shedding by the introduction of thermal buoyancy is shown at relatively low Reynolds numbers (10-40). Hence, depending on the direction of interaction with the free stream flow, the buoyancy sometimes stabilizes the flow and sometimes destabilizes the flow. Accordingly, there is a dual role of superimposed thermal buoyancy in controlling the boundary layer separation around bluff obstacles. Such duality cannot be observed in case of other agents such as rotation, magnetic force which also control the boundary layer separation around bluff obstacles. © 2014 Elsevier Ltd.

Bhattacharya D.,Indian Central Mechanical Engineering Research Institute
Inorganic Chemistry Communications | Year: 2013

A new self-assembled dinuclear rhenium(I) tricarbonyl complex, [Re 2(CO)6(μ-η4-C2O 4)(μ-4,4′-tmdp)] (1) featuring a bis-chelating oxalato dianion (μ-η4-C2O4, H2C 2O4 = oxalic acid) connects two fac-Re(CO)3 cores, which are interconnected by a neutral ditopic N-donor clip ligand, that is, 4,4′-trimethylenedipyridine (μ-4,4′-tmdp) has been elegantly synthesized in high yield in a one-step reaction. Compound 1 was characterized by elemental analysis, IR, ESI-MS, TGA and single-crystal X-ray diffraction analyses. The titled complex represents the first dirhenium(I) metallacycle which shows the coexistence of two emissive pathways at room temperature, one populates an emissive 3π-π* state and the other populates a 3MLCT state. © 2013 Elsevier B.V.

Chatterjee D.,Indian Central Mechanical Engineering Research Institute
Numerical Heat Transfer, Part B: Fundamentals | Year: 2010

A lattice Boltzmann (LB) simulation strategy is proposed for the incompressible transport phenomena occurring during macroscopic solidification of pure substances. The proposed model is derived by coupling a passive scalar-based thermal LB model with the classical enthalpy-porosity technique for solid-liquid phase-transition problems. The underlying hydrodynamics are monitored by a conventional single-particle density distribution function (DF) through a kinetic equation, whereas the thermal field is obtained from another kinetic equation which is governed by a separate temperature DF. The phase-changing aspects are incorporated into the LB model by inserting appropriate source terms in the respective kinetic equations through the most formal technique following the extended Boltzmann equations along with an appropriate enthalpy updating scheme. The proposed model is validated extensively with one- and two-dimensional solidification problems for which analytical and numerical results are available in the literature, and finally, it is used for solving a benchmark problem, the Bridgman crystal growth in a square crucible. Copyright © Taylor & Francis Group, LLC.

Chatterjee D.,Indian Central Mechanical Engineering Research Institute
Numerical Heat Transfer; Part A: Applications | Year: 2010

The fluid flow and heat transfer characteristics around two isothermal square cylinders arranged in a tandem configuration with respect to the incoming flow within an insulated vertical channel at low Reynolds number range (1Re30) are estimated in this article. Spacing between the cylinders (S) is fixed at four widths of the cylinder dimension (d) and, the blockage parameter (B) is set to 0.25. The buoyancy-aided/opposed convection is examined for the Richardson number (Ri) ranges from -1 to 1 with a fixed Prandtl number (Pr) of 0.7. The transient numerical simulation for this two-dimensional, incompressible, laminar flow and heat transfer problem is carried out by a finite volume code based on the PISO algorithm in a collocated grid system. The results suggest that the flow remains steady for the entire range of parameters chosen in this study. The representative streamlines, vorticity, and isotherm patterns are presented to interpret the flow and thermal transport visualization. Additionally, the time average drag coefficient (CD) as well as time and surface average Nusselt number (Nu) for the upstream and downstream cylinders are determined to elucidate the effects of Re and Ri on flow and heat transfer phenomena. Copyright © Taylor & Francis Group, LLC.

Chatterjee D.,Indian Central Mechanical Engineering Research Institute
Numerical Heat Transfer; Part A: Applications | Year: 2013

Numerical simulations are performed to understand the thermo-magneto- convective transport of fluid and heat in a vertical lid-driven square enclosure following a finite volume approach based on the SIMPLEC algorithm. The enclosure is filled with an electrically conducting fluid and having a heated source on the right vertical wall. Two different types of sources, such as a semicircular and a rectangular one, are considered. Both the top and bottom horizontal walls and the right vertical wall, except the source of the enclosure, are assumed insulated and the left vertical wall and the sources are kept isothermal with different temperatures. The left vertical wall is also translating in its own plane at a uniform speed, while all other walls are stationary. Two cases of translational lid motion, viz., vertically upward and downward are considered. A uniform magnetic field is applied along the horizontal direction normal to the translating wall. Shear forces due to lid motion, buoyancy forces as a result of differential heating, and magnetic forces within the electrically conducting fluid act simultaneously. Heat transfer due to forced flow, natural convection, and Joule dissipation are taken into account. Simulations are conducted for various controlling parameters, such as the Rayleigh number (103 ≤ Ra ≤ 105), Hartmann number (0 ≤ Ha ≤ 100), and Joule heating parameter (0 ≤ J ≤ 5), keeping the Reynolds number based on lid velocity fixed as Re = 100. The flow and thermal fields are analyzed through streamline and isotherm plots for various Ha and J. Furthermore, the pertinent transport quantities such as the drag coefficient, Nusselt number, and bulk fluid temperature are also plotted to show the effects of Ha, J, and Ra on them. © 2013 Copyright Taylor and Francis Group, LLC.

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